Cardiac harness for treating congestive heart failure and for defibrillating and/or pacing/sensing

ABSTRACT

A system for treating the heart includes a cardiac harness associated with a cardiac rhythm management devise which includes at least electrodes and a power source. The cardiac harness applies a compressive force on the heart during diastole and systole. The electrodes will deliver an electrical shock to the heart for defibrillation and/or can be used for pacing/sensing. The cardiac harness and electrodes are delivered and implanted on the heart by minimally invasive access.

This application is a division of U.S. Ser. No. 10/704,376 filed Nov. 7,2003, and is co-pending with U.S. Ser. No. 10/777,451 filed Feb. 12,2004; U.S. Ser. No. 10/793,549 filed Mar. 3, 2004; U.S. Ser. No.10/795,574 filed Mar. 5, 2004; and U.S. Ser. No. 10/858,995 filed Jun.2, 2004.

BACKGROUND OF THE INVENTION

The present invention relates to a device for treating heart failure.More specifically, the invention relates to a cardiac harness configuredto be fit around at least a portion of a patient's heart. The cardiacharness includes electrodes attached to a power source for use indefibrillation or pacing.

Congestive heart failure (“CHF”) is characterized by the failure of theheart to pump blood at sufficient flow rates to meet the metabolicdemand of tissues, especially the demand for oxygen. One characteristicof CHF is remodeling of at least portions of a patient's heart.Remodeling involves physical change to the size, shape and thickness ofthe heart wall. For example, a damaged left ventricle may have somelocalized thinning and stretching of a portion of the myocardium. Thethinned portion of the myocardium often is functionally impaired, andother portions of the myocardium attempt to compensate. As a result, theother portions of the myocardium may expand so that the stroke volume ofthe ventricle is maintained notwithstanding the impaired zone of themyocardium. Such expansion may cause the left ventricle to assume asomewhat spherical shape.

Cardiac remodeling often subjects the heart wall to increased walltension or stress, which further impairs the heart's functionalperformance. Often, the heart wall will dilate further in order tocompensate for the impairment caused by such increased stress. Thus, acycle can result, in which dilation leads to further dilation andgreater functional impairment.

Historically, congestive heart failure has been managed with a varietyof drugs. Devices have also been used to improve cardiac output. Forexample, left ventricular assist pumps help the heart to pump blood.Multi-chamber pacing has also been employed to optimally synchronize thebeating of the heart chambers to improve cardiac output. Variousskeletal muscles, such as the latissimus dorsi, have been used to assistventricular pumping. Researches and cardiac surgeons have alsoexperimented with prosthetic “girdles” disposed around the heart. Onesuch design is a prosthetic “sock” or “jacket” that is wrapped aroundthe heart.

Patients suffering from congestive heart failure often are at risk toadditional cardiac failures, including cardiac arrhythmias. When sucharrhythmias occur, the heart must be shocked to return it to a normalcycle, typically by using a defibrillator. Implantablecardioverter/defibrillators (ICD's) are well known in the art andtypically have a lead from the ICD connected to an electrode implantedin the right ventricle. Such electrodes are capable of delivering adefibrillating electrical shock from the ICD to the heart.

Other prior art devices have placed the electrodes on the epicardium atvarious locations, including on or near the epicardial surface of theright and left heart. These devices also are capable of distributing anelectrical current from an implantable cardioverter/defibrillator forpurposes of treating ventricular defibrillation or hemodynamicallystable or unstable ventricular tachyarrhythmias.

Patients suffering from congestive heart failure may also suffer fromcardiac failures, including bradycardia and tachycardia. Such disorderstypically are treated by both pacemakers and implantablecardioverter/defibrillators. The pacemaker is a device that paces theheart with timed pacing pulses for use in the treatment of bradycardia,where the ventricular rate is too slow, or to treat cardiac rhythms thatare too fast, i.e., anti-tachycardia pacing. As used herein, the term“pacemaker” is any cardiac rhythm management device with a pacingfunctionality, regardless of any other functions it may perform such asthe delivery cardioversion or defibrillation shocks to terminate atrialor ventricular fibrillation. Particular forms and uses forpacing/sensing can be found in U.S. Pat. No. 6,574,506 (Kramer et al.)and U.S. Pat. No. 6,223,079 (Bakels et al.); and U.S. Publication No.2003/0130702 (Kramer et al.) and U.S. Publication No. 2003/0195575(Kramer et al.), the entire contents of which are incorporated herein byreference thereto.

The present invention solves the problems associated with prior artdevices relating to a harness for treating congestive heart failure andplacement of electrodes for use in defibrillation, or for use in pacing.

SUMMARY OF THE INVENTION

In accordance with the present invention, a cardiac harness isconfigured to fit at least a portion of a patient's heart and isassociated with one or more electrodes capable of providingdefibrillation or pacing functions. In one embodiment, rows or strandsof undulations are interconnected and associated with coils ordefibrillation and/or pacing/sensing leads. In another embodiment, thecardiac harness includes a number of panels separated by coils orelectrodes, wherein the panels have rows or strands of undulationsinterconnected together so that the panels can flex and can expand andretract circumferentially. The panels of the cardiac harness are coatedwith a dielectric coating to electrically insulate the panels from anelectrical shock delivered through the electrodes. Further, theelectrodes are at least partially coated with a dielectric material toinsulate the electrodes from the cardiac harness. In one embodiment, thestrands or rows of undulations are formed from Nitinol and are coatedwith a dielectric material such as silicone rubber. In this embodiment,the electrodes are at least partially coated with the same dielectricmaterial of silicone rubber. The electrode portion of the leads are notcovered by the dielectric material so that as the electrical shock isdelivered by the electrodes to the epicardial surface of the heart, thecoated panels and the portion of the electrodes that are coated areinsulated by the silicone rubber. In other words, the heart received anelectrical shock only where the bare metal of the electrodes are incontact with or are adjacent to the epicardial surface of the heart. Thedielectric coating also serves to attach the panels to the electrodes.

In another embodiment, the electrodes have a first surface and a secondsurface, the first surface being in contact with the outer surface ofthe heart, such as the epicardium, and the second surface faces awayfrom the heart. Both the first surface and the second surface do nothave a dielectric coating so that an electrical charge can be deliveredto the outer surface of the heart for defibrillating or for pacing. Inthis embodiment, at least a portion of the electrodes are coated with adielectric coating, such as silicone rubber, parylene or polyurethane.The dielectric coating serves to insulate the bare metal portions of theelectrode from the cardiac harness, and also to provide attachment meansfor attaching the electrodes to the panels of the cardiac harness.

The number of electrodes and the number of panels forming the cardiacharness is a matter of choice. For example, in one embodiment thecardiac harness can include two panels separated by two electrodes. Theelectrodes would be positioned 180° apart, or in some other orientationso that the electrodes could be positioned to provide a optimumelectrical shock to the epicardial surface of the heart, preferablyadjacent the right ventricle or the left ventricle. In anotherembodiment, the electrodes can be positioned 180° apart so that theelectrical shock carries through the myocardium adjacent the rightventricle thereby providing an optimal electrical shock fordefibrillation or periodic shocks for pacing. In another embodiment,three leads are associated with the cardiac harness so that there arethree panels separated by the three electrodes.

In yet another embodiment, four panels on the cardiac harness areseparated by four electrodes. In this embodiment, two electrodes arepositioned adjacent the left ventricle on or near the epicardial surfaceof the heart while the other two electrodes are positioned adjacent theright ventricle on or near the epicardial surface of the heart. As anelectrical shock is delivered, it passes through the myocardium betweenthe two sets of electrodes to shock the entire ventricles.

In another embodiment, there are more than four panels and more thanfour electrodes forming the cardiac harness. Placement of the electrodesand the panels is a matter of choice. Further, one or more electrodesmay be deactivated.

In another embodiment, the cardiac harness includes multiple electrodesseparating multiple panels. The embodiment also includes one or morepacing/sensing electrodes (multi-site) for use in sensing heartfunctions, and delivering pacing stimuli for resynchronization,including biventricular pacing and left ventricle pacing or rightventricular pacing.

In each of the embodiments, an electrical shock for defibrillation, oran electrical pacing stimuli for synchronization or pacing is deliveredby a pulse generator, which can include an implantablecardioverter/defibrillator (ICD), a cardiac resynchronization therapydefibrillator (CRT-D), and/or a pacemaker. Further, in each of theforegoing embodiments, the cardiac harness can be coupled with multiplepacing/sensing electrodes to provide multi-site pacing to controlcardiac function. By incorporating multi-site pacing into the cardiacharness, the system can be used to treat contractile dysfunction whileconcurrently treating bradycardia and tachycardia. This will improvepumping function by altering heart chamber contraction sequences whilemaintaining pumping rate and rhythm. In one embodiment, the cardiacharness incorporates pacing/sensing electrodes positioned on theepicardial surface of the heart adjacent to the left and right ventriclefor pacing both the left and right ventricles.

In another embodiment, the cardiac harness includes multiple electrodesseparating multiple panels. In this embodiment, at least some of theelectrodes are positioned on or near (proximate) the epicardial surfaceof the heart for providing an electrical shock for defibrillation, andother of the electrodes are positioned on the epicardial surface of theheart to provide pacing stimuli useful in synchronizing the left andright ventricles, cardiac resynchronization therapy, and biventricularpacing or left ventricular pacing or right ventricular pacing.

In another embodiment, the cardiac harness includes multiple electrodesseparating multiple panels. At least some of the electrodes provide anelectrical shock for defibrillation, and one of the electrodes, a singlesite electrode, is used for pacing and sensing a single ventricle. Forexample, the single site electrode is used for left ventricular pacingor right ventricular pacing. The single site electrode also can bepositioned near the septum in order to provide bi-ventricular pacing.

In yet another embodiment, the cardiac harness includes one or moreelectrodes associated with the cardiac harness for providing apacing/sensing function. In this embodiment, a single site electrode ispositioned on the epicardial surface of the heart adjacent the leftventricle for left ventricular pacing. Alternatively, a single siteelectrode is positioned on the surface of the heart adjacent the rightventricle to provide right ventricular pacing. Alternatively, more thanone pacing/sensing electrode is positioned on the epicardial surface ofthe heart to treat synchrony of both ventricles, includingbi-ventricular pacing.

In another embodiment, the cardiac harness includes coils that separatemultiple panels. The coils have a high degree of flexibility, yet arecapable of providing column strength so that the cardiac harness can bedelivered by minimally invasive access.

All embodiments of the cardiac harness, including those with electrodes,are configured for delivery and implantation on the heart usingminimally invasive approaches involving cardiac access through, forexample, subxiphoid, subcostal, or intercostal incisions, and throughthe skin by percutaneous delivery using a catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic view of a heart with a prior art cardiacharness placed thereon.

FIGS. 2A–2B depict a spring hinge of a prior art cardiac harness in arelaxed position and under tension.

FIG. 3 depicts a prior art cardiac harness that has been cut out of aflat sheet of material.

FIG. 4 depicts the prior art cardiac harness of FIG. 3 formed into ashape configured to fit about a heart.

FIG. 5A depicts a flattened view of one embodiment of the cardiacharness of the invention showing two panels connected to two electrodes.

FIG. 5B depicts a cross-sectional view of an electrode.

FIG. 5C depicts a cross-sectional view of an electrode.

FIG. 5D depicts a cross-sectional view of an electrode.

FIG. 6A depicts a cross-sectional view of an undulating strand or ring.

FIG. 6B depicts a cross-sectional view of an undulating strand or ring.

FIG. 6C depicts a cross-sectional view of an undulating strand or ring.

FIG. 7A depicts an enlarged plan view of a cardiac harness showing threeelectrodes separating three panels, with the far side panel not shownfor clarity.

FIG. 7B depicts an enlarged partial plan view of the cardiac harness ofFIG. 7A showing an electrode partially covered with a dielectricmaterial which also serves to attach the panels to the electrode.

FIG. 8A depicts a transverse cross-sectional view of the heart showingthe position of electrodes for defibrillation and/or pacing/sensingfunctions.

FIG. 8B depicts a transverse cross-sectional view of the heart showingthe position of electrodes for defibrillation and/or pacing/sensingfunctions.

FIG. 8C depicts a transverse cross-sectional view of the heart showingthe position of electrodes for defibrillation and/or pacing/sensingfunctions.

FIG. 8D depicts a transverse cross-sectional view of the heart showingthe position of electrodes for defibrillation and/or pacing/sensingfunctions.

FIG. 9 depicts a plan view of one embodiment of a cardiac harness havingpanels separated by and attached to flexible coils.

FIG. 10 depicts a flattened plan view of a cardiac harness similar tothat of FIG. 9 but with fewer panels and coils.

FIG. 11 depicts a plan view of one embodiment of a cardiac harnesshaving panels separated by and attached to flexible coils.

FIG. 12 depicts a plan view of a cardiac harness similar to that shownin FIG. 11 mounted on the epicardial surface of the heart.

FIG. 13 depicts a perspective view of a cardiac harness similar to thatof FIG. 9 where the harness has been folded to reduce its profile forminimally invasive delivery.

FIG. 14 depicts the cardiac harness of FIG. 13 in a partially bent andfolded condition to reduce its profile for minimally invasive delivery.

FIG. 15A depicts an enlarged plan view of a cardiac harness showingcontinuous undulating strands with electrodes overlaying the strands.

FIG. 15B depicts an enlarged partial plan view of the cardiac harness ofFIG. 15A showing continuous undulating strands with an electrodeoverlying the strands.

FIG. 15C depicts a partial cross-sectional view taken along lines15C—15C showing the electrode and undulating strands.

FIG. 15D depicts a partial cross-sectional view taken along lines15D—15D showing the undulating strands in notches in the electrode.

FIG. 16 depicts a top view of a fixture for winding wire to constructthe cardiac harness.

FIG. 17 depicts a plan view of a portion of a cardiac harness showingpanels separated by electrodes.

FIGS. 18A, 18B and 18C depict various views of a mold used for injectinga dielectric material around the cardiac harness and the electrodes.

FIGS. 19A, 19B and 19C depict various views of molds used in injecting adielectric material around the cardiac harness and the electrodes.

FIG. 20 depicts a top view of a portion of an electrode having ametallic coil winding.

FIG. 21 depicts a side view of the electrode portion shown in FIG. 20.

FIG. 22 depicts a cross-sectional view taken along lines 22—22 showinglumens extending through the electrode.

FIG. 23 depicts a cross-sectional view taken along lines 23—23 depictinganother embodiment of lumens extending through the electrode.

FIG. 24 depicts a top view of a portion of an electrode having multiplecoil windings.

FIG. 25A depicts a side view of a portion of a defibrillator electrodecombined with a pacing/sensing electrode.

FIG. 25B depicts a top view of the electrode portion of FIG. 25A.

FIGS. 26A–26C depict various views of a defibrillator electrode combinedwith a pacing/sensing electrode.

FIG. 27 depicts a side view of an introducer for delivering the cardiacharness through minimally invasive procedures.

FIG. 28 depicts a perspective end view of a dilator with the cardiacharness releasably positioned therein.

FIG. 29 depicts an end view of the introducer with the cardiac harnessreleasably positioned therein.

FIG. 30 depicts a schematic cross-sectional view of a human thorax withthe cardiac harness system being delivered by a delivery device insertedthrough an intercostal space and contacting the heart.

FIG. 31 depicts a plan view of the heart with a suction devicereleasably attached to the apex of the heart.

FIG. 32 depicts a plan view of the heart with the suction deviceattached to the apex and the introducer positioned to deliver thecardiac harness over the heart.

FIG. 33 depicts a plan view of the cardiac harness being deployed fromthe introducer onto the epicardial surface of the heart.

FIG. 34 depicts a plan view of the heart with the cardiac harness beingdeployed from the introducer onto the epicardial surface of the heart.

FIG. 35 depicts a plan view of the heart with the cardiac harness havingelectrodes attached thereto, surrounding a portion of the heart.

FIG. 36 depicts a schematic view of the cardiac harness assembly mountedon the human heart together with leads and an ICD for use indefibrillation or pacing.

FIG. 37 depicts an exploded a side view of a delivery system with theintroducer tube, dilator tube, and ejection tube shown prior toassembly.

FIG. 38 depicts a cross-sectional view of the introducer tube takenalong lines 38—38.

FIG. 39 depicts a cross-sectional view taken along lines 39—39 showingthe cross-section of the dilator tube.

FIG. 40 depicts a cross-sectional view taken along lines 40—40 extendingthrough the plate of the ejection tube and showing the various lumens inthe plate.

FIG. 41 depicts a cross-sectional view taken along lines 41—41 of theproximal end of the ejection tube.

FIG. 42 depicts a longitudinal cross-sectional view and schematic of theejection tube with the leads from the electrodes extending through thelumens in the plate and the tubing from the suction cup extendingthrough a lumen in the plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention relates to a method and apparatus for treating heartfailure. It is anticipated that remodeling of a diseased heart can beresisted or even reversed by alleviating the wall stresses in such aheart. The present invention discloses embodiments and methods forsupporting the cardiac wall and for providing defibrillation and/orpacing functions using the same system. Additional embodiments andaspects are also discussed in Applicants' co-pending applicationentitled “Multi-Panel Cardiac Harness” U.S. Ser. No. 60/458,991 filedMar. 28, 2003, the entirety of which is hereby expressly incorporated byreference.

Prior Art Devices

FIG. 1 illustrates a mammalian heart 10 having a prior art cardiac wallstress reduction device in the form of a harness applied to it. Theharness surrounds a portion of the heart and covers the right ventricle11, the left ventricle 12, and the apex 13. For convenience ofreference, longitudinal axis 15 goes through the apex and the AV groove14. The cardiac harness has a series of hinges or spring elements thatcircumscribe the heart and, collectively, apply a mild compressive forceon the heart to alleviate wall stresses.

The term “cardiac harness” as used herein is a broad term that refers toa device fit onto a patient's heart to apply a compressive force on theheart during at least a portion of the cardiac cycle.

The cardiac harness illustrated in FIG. 1 has at least one undulatingstrand having a series of spring elements referred to as hinges orspring hinges that are configured to deform as the heart expands duringfilling. Each hinge provides substantially unidirectional elasticity, inthat it acts in one direction and does not provide as much elasticity inthe direction perpendicular to that direction. For example, FIG. 2Ashows a prior art hinge member at rest. The hinge member has a centralportion and a pair of arms. As the arms are pulled, as shown in FIG. 2B,a bending moment is imposed on the central portion. The bending momenturges the hinge member back to its relaxed condition. Note that atypical strand comprises a series of such hinges, and that the hingesare adapted to elastically expand and retract in the direction of thestrand.

In the harness illustrated in FIG. 1, the strands of spring elements areconstructed of extruded wire that is deformed to form the springelements.

FIGS. 3 and 4 illustrate another prior art cardiac harness, shown at twopoints during manufacture of such a harness. The harness is first formedfrom a relatively thin, flat sheet of material. Any method can be usedto form the harness from the flat sheet. For example, in one embodiment,the harness is photochemically etched from the material; in anotherembodiment, the harness is laser-cut from the thin sheet of material.The harness shown in FIGS. 3 and 4 has been etched from a thin sheet ofNitinol, which is superelastic material that also exhibits shape memoryproperties. The flat sheet of material is draped over a form, die or thelike, and is formed to generally take on the shape of at least a portionof a heart.

With further reference to FIGS. 1 and 4, the cardiac harnesses have abase portion which is sized and configured to generally engage and fitonto a base region of a patient's heart, an apex portion which is sizedand shaped so as to generally engage and fit on an apex region of apatient's heart, and a medial portion between the base and apexportions.

In the harness shown in FIGS. 3 and 4, the harness has strands or rowsof undulating wire. As discussed above, the undulations havehinge/spring elements which are elastically bendable in a desireddirection. Some of the strands are connected to each other byinterconnecting elements. The interconnecting elements help maintain theposition of the strands relative to one another. Preferably theinterconnecting elements allow some relative movement between adjacentstrands.

The undulating spring elements exert a force in resistance to expansionof the heart. Collectively, the force exerted by the spring elementstends toward compressing the heart, thus alleviating wall stresses inthe heart as the heart expands. Accordingly, the harness helps todecrease the workload of the heart, enabling the heart to moreeffectively pump blood through the patient's body and enabling the heartan opportunity to heal itself. It should be understood that severalarrangements and configurations of spring members can be used to createa mildly compressive force on the heart to reduce wall stresses. Forexample, spring members can be disposed over only a portion of thecircumference of the heart or the spring members can cover a substantialportion of the heart.

As the heart expands and contracts during diastole and systole, thecontractile cells of the myocardium expand and contract. In a diseasedheart, the myocardium may expand such that the cells are distressed andlose at least some contractility. Distressed cells are less able to dealwith the stresses of expansion and contraction. As such, theeffectiveness of heart pumping decreases. Each series of spring hingesof the above cardiac harness embodiments is configured so that as theheart expands during diastole the spring hinges correspondingly willexpand, thus storing expansion forces as bending energy in the spring.As such, the stress load on the myocardium is partially relieved by theharness. This reduction in stress helps the myocardium cells to remainhealthy and/or regain health. As the heart contracts during systole, thedisclosed prior art cardiac harnesses apply a moderate compressive forceas the hinge or spring elements release the bending energy developedduring expansion allowing the cardiac harness to follow the heart as itcontracts and to apply contractile force as well.

Other structural configurations for cardiac harnesses exist, however,but all have drawbacks and do not function optimally to treat CHF andother related diseases or failures. The present invention cardiacharness provides a novel approach to treat CHF and provides electrodesassociated with the harness to deliver an electrical shock fordefibrillation or a pacing stimulus for resynchronization, or forbiventricular pacing/sensing.

The Present Invention Embodiments

The present invention is directed to a cardiac harness system fortreating the heart. The cardiac harness system of the present inventioncouples a cardiac harness for treating the heart coupled with a cardiacrhythm management device. More particularly, the cardiac harnessincludes rows or undulating strands of spring elements that provide acompressive force on the heart during diastole and systole in order torelieve wall stress pressure on the heart. Associated with the cardiacharness is a cardiac rhythm management device for treating any number ofirregularities in heart beat due to, among other reasons, congestiveheart failure. Thus, the cardiac rhythm management device associatedwith the cardiac harness can include one or more of the following: animplantable cardioverter/defibrillator with associated leads andelectrodes; a cardiac pacemaker including leads and electrodes used forsensing cardiac function and providing pacing stimuli to treat synchronyof both vessels; and a combined implantable cardioverter/defibrillatorand pacemaker, with associated leads and electrodes to provide adefibrillation shock and/or pacing/sensing functions.

The cardiac harness system includes various configurations of panelsconnected together to at least partially surround the heart and assistthe heart during diastole and systole. The cardiac harness system alsoincludes one or more leads having electrodes associated with the cardiacharness and a source of electrical energy supplied to the electrodes fordelivering a defibrillating shock or pacing stimuli.

In one embodiment of the invention, as shown in a flattenedconfiguration in FIG. 5, a cardiac harness 20 includes two panels 21 ofgenerally continuous undulating strands 22. A panel includes rows orundulating strands of hinges or spring elements that are connectedtogether and that are positioned between a pair of electrodes, the rowsor undulations being highly elastic in the circumferential directionand, to a lesser extent, in the longitudinal direction. In thisembodiment, the undulating strands have U-shaped hinges or springelements 23 capable of expanding and contracting circumferentially alongdirectional line 24. The cardiac harness has a base or upper end 25 andan apex or lower end 26. The undulating strands are highly elastic inthe circumferential direction when placed around the heart 10, and to alesser degree in a direction parallel to the longitudinal axis 15 of theheart. Similar hinges or spring elements are disclosed in co-pending andco-assigned U.S. Ser. No. 60/458,991 filed Mar. 28, 2003, the entirecontents of which are incorporated herein by reference. While the FIG. 5embodiment appears flat for ease of reference, in use it issubstantially cylindrical (or tapered) to conform to the heart and theright and left side panels would actually be one panel and there wouldbe no discontinuity in the undulating strands.

The undulating strands 22 provide a compressive force on the epicardialsurface of the heart thereby relieving wall stress. In particular, thespring elements 23 expand and contract circumferentially as the heartexpands and contracts during the diastolic and systolic functions. Asthe heart expands, the spring elements expand and resist expansion asthey continue to open and store expansion forces. During systole, as theheart 10 contracts, the spring elements will contract circumferentiallyby releasing the stored bending forces thereby assisting in both thediastolic and systolic function.

As just discussed, bending stresses are absorbed by the spring elements23 during diastole and are stored in the elements as bending energy.During systole, when the heart pumps, the heart muscles contract and theheart becomes smaller. Simultaneously, bending energy stored within thespring elements 23 is at least partially released, thereby providing anassist to the heart during systole. In a preferred embodiment, thecompressive force exerted on the heart by the spring elements of theharness comprises about 10% to 15% of the mechanical work done as theheart contracts during systole. Although the harness is not intended toreplace ventricular pumping, the harness does substantially assist theheart during systole.

The undulating strands 22 can have varying numbers of spring element 23depending upon the amplitude and pitch of the spring elements. Forexample, by varying the amplitude of the pitch of the spring elements,the number of undulations per panel will vary as well. It may be desiredto increase the amount of compressive force the cardiac harness 20imparts on the epicardial surface of the heart, therefore the presentinvention provides for panels that have spring elements with loweramplitudes and a shorter pitch, thereby increasing the expansion forceimparted by the spring element. In other words, all other factors beingconstant, a spring element having a relatively lower amplitude will bemore rigid and resist opening, thereby storing more bending forcesduring diastole. Further, if the pitch is smaller, there will be morespring elements per unit of length along the undulating strand, therebyincreasing the overall bending force stored during diastole, andreleased during systole. Other factors that will affect the compressiveforce imparted by the cardiac harness onto the epicardial surface of theheart include the shape of the spring elements, the diameter and shapeof the wire forming the undulating strands, and the material comprisingthe strands.

As shown in FIG. 5, the undulating strands 22 are connected to eachother by grip pads 27. In the embodiments shown in FIG. 5, adjacentundulating strands are connected by one or more grip pads attached atthe apex 28 of the spring elements 23. The number of grip pads betweenadjacent undulating strands is a matter of choice and can range from onegrip pad between adjacent undulating strands, to one grip pad for everyapex on the undulating strand. Importantly, the grip pads should bepositioned in order to maintain flexibility of the cardiac harness 20without sacrificing the objectives of maintaining the spacing betweenadjacent undulating strands to prevent overlap and to enhance thefrictional engagement between the grip pads and the epicardial surfaceof the heart. Further, while it is desirable to have the grip padsattached at the apex of the spring elements, the invention is not solimited. The grip pads 27 can be attached anywhere along the length ofthe spring elements, including the sides 29. Further, the shape of thegrip pads 27, as shown in FIG. 5, can vary to suit a particular purpose.For example, grip pad 27 can be attached to the apex 28 of oneundulating strand 22, and be attached to two apices on an adjacentundulating strand (see FIG. 7). As shown in FIG. 5, all of the apicespoint toward each other, and are said to be “out-of-phase.” If theapices of the undulations were aligned, they would be “in-phase.” Theapices are all out-of-phase since the number of spring elements in eachundulating strand is the same, however, the invention contemplates thatthe number of spring elements in each undulating strand may vary sincethe heart is tapered from its base near the top to its apex 13 at thebottom. Thus, there would be more spring elements and a longerundulating strand per panel at the top or base of the cardiac harnessthan at the bottom of the cardiac harness near the apex of the heart.Accordingly, the cardiac harness would be tapered from the relativelywide base to a relatively narrow bottom toward the apex of the heart,and this would affect the alignment of the apices of the springelements, and hence the ability of the grip pads 27 to align perfectlyand attach to adjacent apices of the spring elements. A furtherdisclosure and embodiments relating to the undulating strands and theattachment means in the form of grip pads is found in co-pending andco-assigned U.S. Ser. No. 60/486,062 filed Jul. 10, 2003, the entirecontents of which are incorporated herein by reference. While theconnections between adjacent undulating strands 22 is preferably grippads 27, in an alternative embodiment (not shown) the undulating strandsare connected by interconnecting elements made of the same material asthe strands. The interconnecting elements can be straight or curved asshown in FIGS. 8A–8B of commonly owned U.S. Pat. No. 6,612,979 B2, theentire contents of which is incorporated by reference herein.

It is preferred that the undulating strands 22 be continuous as shown inFIG. 5. For example, every pair of adjacent undulating strands areconnected by bar arm 30. It is preferred that the bar arms form part ofa continuous wire that is bent to form the undulating strands, and thenwelded at its ends along the bar arm. The weld is not shown in FIG. 5,but can be by any conventional method such as laser welding, fusionbonding, or conventional welding. The type of wire used to form theundulating strands may have a bearing on the method of attaching theends of the wire used to form the undulating strand. For example, it ispreferred that the undulating strands be made out of a nickel-titaniumalloy, such as Nitinol, which may lose some of its superelastic or shapememory properties if exposed to high heat during conventional welding.

Associated with the cardiac harness of the present invention is acardiac rhythm management device as previously disclosed. Thus,associated with the cardiac harness as shown in FIG. 5, are one or moreelectrodes for use in providing defibrillating shock. As can be seenimmediately below, any number of factors associated with congestiveheart failure can lead to fibrillation, acquiring immediate action tosave the patient's life.

Diseased hearts often have several maladies. One malady that is notuncommon is irregularity in heartbeat caused by irregularities in theelectrical stimulation system of the heart. For example, damage from acardiac infarction can interrupt the electrical signal of the heart. Insome instances, implantable devices, such as pacemakers, help toregulate cardiac rhythm and stimulate heart pumping. A problem with theheart's electrical system can sometimes cause the heart to fibrillate.During fibrillation, the heart does not beat normally, and sometimesdoes not pump adequately. A cardiac defibrillator can be used to restorethe heart to normal beating. An external defibrillator typicallyincludes a pair of electrode paddles applied to the patient's chest. Thedefibrillator generates an electric field between electrodes. Anelectric current passes through the patient's heart and stimulates theheart's electrical system to help restore the heart to regular pumping.

Sometimes a patient's heart begins fibrillating during heart surgery orother open-chest surgeries. In such instances, a special type ofdefibrillating device is used. An open-chest defibrillator includesspecial electrode paddles that are configured to be applied to the hearton opposite sides of the heart. A strong electric field is createdbetween the paddles, and an electric current passes though the heart todefibrillate the heart and restore the heart to regular pumping.

In some patients that are especially vulnerable to fibrillation, animplantable heart defibrillation device may be used. Typically, animplantable heart defibrillation device includes an implantablecardioverter defibrillator (ICD) or a cardiac resynchronization therapydevice (CRT-D) which usually has only one electrode positioned in theright ventricle, and the return electrode is the defibrillator housingitself, typically implanted in the pectoral region. Alternatively, animplantable device includes two or more electrodes mounted directly on,in or adjacent the heart wall. If the patient's heart beginsfibrillating, these electrodes will generate an electric fieldtherebetween in a manner similar to the other defibrillators discussedabove.

Testing has indicated that when defibrillating electrodes are appliedexternal to a heart that is surrounded by a device made of electricallyconductive material, at least some of the electrical current disbursedby the electrodes is conducted around the heart by the conductivematerial, rather than through the heart. Thus, the efficacy ofdefibrillation is reduced. Accordingly, the present invention includesseveral cardiac harness embodiments that enable defibrillation of theheart and other embodiments disclose means for defibrillating,resynchronization, left ventricular pacing, right ventricular pacing,and biventricular pacing/sensing.

In further keeping with the invention, the cardiac harness 20 includes apair of leads 31 having conductive electrode portions 32 that are spacedapart and which separate panels 21. As shown in FIG. 5, the electrodesare formed of a conductive coil wire 33 that is wrapped around anon-conductive member 34, preferably in a helical manner. A conductivewire 35 is attached to the coil wire and to a power source 36. As usedherein, the power source 36 can include any of the following, dependingupon the particular application of the electrode: a pulse generator; animplantable cardioverter/defibrillator; a pacemaker; and an implantablecardioverter/defibrillator coupled with a pacemaker. In the embodimentshown in FIG. 5, the electrodes are configured to deliver an electricalshock, via the conductive wire and the power source, to the epicardialsurface of the heart so that the electrical shock passes through themyocardium. Even though the electrodes are spaced so that they would beabout 180° apart around the circumference of the heart in the embodimentshown, they are not so limited. In other words, the electrodes can bespaced so that they are about 45° apart, 60° apart, 90° apart, 120°apart, or any arbitrary arc length spacing, or, for that matter,essentially any arc length apart around the circumference of the heartin order to deliver an appropriate electrical shock. As previouslydescribed, it may become necessary to defibrillate the heart and theelectrodes 32 are configured to deliver an appropriate electrical shockto defibrillate the heart.

Still referring to FIG. 5, the electrodes 32 are attached to the cardiacharness 20, and more particularly to the undulating strands 22, by adielectric material 37. The dielectric material insulates the electrodesfrom the cardiac harness so that electrical current does not pass fromthe electrode to the harness thereby undesirably shunting current awayfrom the heart for defibrillation. Preferrably, the dielectric materialcovers the undulating strands 22 and covers at least a portion of theelectrodes 32. In the FIG. 5 embodiment, the middle panel undulatingstrands are covered with the dielectric material while the right andleft side panels are bare metal. While it is preferred that all of theundulating strands of the panels be coated with the dielectric material,thereby insulating the harness from the electric shock delivered by theelectrodes, some or all of the undulating strands can be bare metal usedto deliver the electrical shock to the epicardial surface of the heartfor defibrillation or for pacing.

As will be described in more detail, the electrodes 32 have a conductivedischarge first surface 38 that is intended to be proximate to or indirect contact with the epicardial surface of the heart, and aconductive discharge second surface 39 that is opposite to the firstsurface and faces away from the heart surface. As used herein, the term“proximate” is intended to mean that the electrode is positioned near orin direct contact with the outer surface of the heart, such as theepicardial surface of the heart. The first surface and second surfacetypically will not be covered with the dielectric material 37 so thatthe bare metal conductive coil can transmit the electrical current fromthe power source (pulse generator), such as an implantablecardioverter/defibrillator (ICD or CRT-D) 36, to the epicardial surfaceof the heart. In an alternative embodiment, either the first or thesecond surface may be covered with dielectric material in order topreferentially direct the current through only one surface. Furtherdetails of the construction and use of the leads 31 and electrodes 33 ofthe present invention, in conjunction with the cardiac harness, will bedescribed more fully herein.

Importantly, the dielectric material 37 used to attach the electrodes 32to the undulating strands 22 insulates the undulating strands from anyelectrical current discharged through the conductive metal coils 33 ofthe electrodes. Further, the dielectric material in this embodiment isflexible so that the electrodes can serve as a seam or hinge to fold thecardiac harness 20 into a lower profile for minimally invasive delivery.Thus, as will be described in more detail (see FIGS. 13 and 14), thecardiac harness can be folded along its length, along the length of theelectrodes, in order to reduce the profile for intercostal delivery, forexample through the rib cage or other area typically used for minimallyinvasive surgery for accessing the heart. Minimally invasive approachesinvolving the heart typically are made through subxiphoid, subcostal orintercostal incisions. When the cardiac harness is folded, it can bereduced into a circular or a more or less oval shape, both of whichpromote minimally invasive procedures.

In further keeping with the invention, cross sectional views of theleads 31 and the electrode portion 32 are shown in FIGS. 5B, 5C, and 5D.As shown in FIG. 5B, the electrode 32 has the coil wire 33 wrappedaround the non-conducting member 34 in a helical pattern. The dielectricmaterial 37 provides a spaced connection between the electrode and thebar arms 30 at the ends of the undulating strands 22. The electrodes donot touch or overlap with the bar arms or any portion of the undulatingstrands. Instead, the dielectric material provides the attachment meansbetween the electrodes and the bar arms of the undulating strands. Thus,the dielectric material 37 not only acts as an insulating non-conductivematerial, but also provides attachment means between the undulatingstrands and the electrodes. Because the dielectric material 37 isrelatively thin at the attachment points, it is highly flexible andpermits the electrodes to be flexible along with the cardiac harnesspanels 21, which will expand and contract as the heart beats aspreviously described.

Referring to FIG. 5C, the non-conductive member 34 extends beyond thecoil wire 33 for a distance. The non-conductive member preferably ismade from the same material as the dielectric material 37, typically asilicone rubber or similar material. While it is preferred that thedielectric material be made from silicone rubber, or a similar material,it also can be made from parylene (Union Carbide), polyurethanes, PTFE,TFE, and ePTFE. As can be seen, the non-conductive member providessupport for the dielectric material to attach the bar arms 30 of theundulating strands 22 in order to connect the strands to the electrode32. A conductive wire 35 extends through the non-conducting member andattaches to the proximal end of the coil wire 33 so that when anelectrical current is delivered from the power source 36 throughconductive wire 35, the electrode coil 33 will be energized. Theconductive wire 35 is also covered by non-conducting material 34.Referring to FIG. 5D, it can be seen that the non-conductive member 34continues to extend beyond the bottom (apex) of the cardiac harness andthat conductive wire 35 continues to extend out of the non-conductivemember and into the power source 36. In the embodiment shown in FIGS.5B–5D, the cardiac harness is insulated from the electrodes by thedielectric material 37 so that there is no shunting of electricalcurrents by the cardiac harness 20 from the electrical shock deliveredby the electrodes during defibrillation or pacing functions.

While it is preferred that the cardiac harness 20 be comprised ofundulating strands 22 made from a solid wire member, such as asuperelastic or shape memory material such as Nitinol, and be insulatedfrom the electrodes 32, it is possible to use some or all of theundulating strands to deliver the electrical shock to the epicardialsurface of the heart. For example, as shown in FIG. 6A, a composite wire45 can be used to form the undulating strands 22 and, importantly, toeffectively transmit current to deliver an electrical shock to theepicardial surface of the heart. The composite wire 45 includes acurrent conducting wire 47 made from, for example silver (Ag), and whichis covered by a Nitinol tube 46. In order to improve the surfaceconductivity of the outer Nitinol tube 46, a highly conductive coatingis placed on the Nitinol tube. For example, the Nitinol tube can becovered with a deposition layer of platinum (Pt) or platinum-iridium(Pt—Ir), or an equivalent material including iridium oxide (IROX). Thecomposite wire, so constructed, will have superior mechanicalperformance to expand and contract due to the Nitinol tubing, and alsowill have improved electrical properties resulting from the currentconducting wire 47 and improved electrolytic/electrochemical propertiesvia the surface layer of platinum-iridium. Thus, if some portion or allof the undulating strands 22 are made from a composite wire 45, thecardiac harness 20 will be capable of delivering a defibrillating shockon selected portions of the heart via the undulating strands and willalso function to impart compressive forces as previously described.

In contrast to the current conducting undulating strands of FIG. 6A, arethe non-conducting insulated undulating strands 22 as shown by crosssectional view FIG. 6B. As previously described, some or all of theundulating strands 22 can be covered with dielectric material 37 inorder to insulate the strands from the electrical current deliveredthrough the electrodes while delivering shock on the epicardial surfaceof the heart. Thus, as shown in FIG. 6B, the undulating strands 22 arecovered by dielectric material 37 to provide insulation from theelectrical shock delivered by the electrodes 32, yet maintain theflexibility and the expansive properties of the undulating strands.

An important aspect of the invention is to provide a cardiac harness 20that can be implanted minimally invasively and be attached to theepicardial surface of the heart, without requiring sutures, clips,screws, glue or other attachment means. Importantly, the undulatingstrands 22 may provide relatively high frictional engagement with theepicardial surface, depending on the cross-sectional shape of thestrands. For example, in the embodiment disclosed in FIG. 6C, thecross-sectional shape of the undulating strands 22 can be circular,rectangular, triangular or for that matter, any shape that increases thefrictional engagement between the undulating strands and the epicardialsurface of the heart. As shown in FIG. 6C, the middle cross-section viewhaving a flat rectangular surface (wider than tall) not only has a lowprofile for enhancing minimally invasive delivery of the cardiacharness, but it also has rectangular edges that may have a tendency toengage and dig into the epicardium to increase the frictional engagementwith the epicardial surface of the heart. With the propercross-sectional shape for the undulating strands, coupled with the grippads 27 having a high frictional engagement feature, the necessity forsuturing, clipping, or further attachment means to attach the cardiacharness to the epicardial surface of the heart becomes unnecessary.

In another embodiment as shown in FIGS. 7A and 7B, a differentconfiguration for cardiac harness 20 and the electrodes 32 are shown, ascompared to the FIG. 5 embodiments. In FIGS. 7A and 7B, three electrodesare shown separating the three panels 21 with undulating strands 22extending between the electrodes. As with previous embodiments, springs23 are formed by the undulating strands so that the undulating strandscan expand and contract during the diastolic and systolic functions, andapply a compressive force during both functions. The far side panel ofFIG. 7A is not shown for clarity purposes. The position of theelectrodes around the circumference of the heart is a matter of choice,and in the embodiment of FIG. 7A, the electrodes can be spaced an equaldistance apart at about 120°. Alternatively, it may be important todeliver the electrical shock more through the right ventricle requiringthe positioning of the electrodes closer to the right ventricle than tothe left ventricle. Similarly, it may be more important to deliver anelectrical shock to the left ventricle as opposed to the rightventricle. Thus, positioning of electrodes, as with other embodiments,is a matter of choice.

Still referring to FIGS. 7A and 7B, in this embodiment electrodes 32extend beyond the bottom or apex portion of the cardiac harness 20 inorder to insure that the electrical shock delivered by the electrodes isdelivered to the epicardial surface of the heart and including the lowerportion of the heart closer to the apex 13. Thus, the electrodes 22 havea distal end 50 and a proximal end 51 where the proximal end ispositioned closer to the apex 13 of the heart and the distal end ispositioned closer to the base or upper portion of the heart. As usedherein, distal is intended to mean further into the body and away fromthe attending physician, and proximal is meant to be closer to theoutside of the body and closer to the attending physician. The proximalends of the electrodes are positioned closer to the apex of the heartand provide several functions, including the ability to deliver anelectrical shock closer to the apex of the heart. The electrode proximalends also function to provide support for the cardiac harness 20 and thepanels 21, and lend support not only during delivery (as will be furtherdescribed herein) but in separating the panels and in gripping theepicardial surface of the heart to retain the harness on the heartwithout slipping.

While the FIGS. 7A and 7B embodiments show electrodes 32 separatingthree panels 21 of the cardiac panel 20, more or fewer electrodes andpanels can be provided to suit a particular application. For example, inone preferred embodiment, four electrodes 32 separate four panels 21, sothat two of the electrodes can be positioned on opposite sides of theleft ventricle and two of the electrodes can be positioned on oppositesides of the right ventricle. In this embodiment, preferably all fourelectrodes would be used, with a first set of two electrodes on oppositesides of the right ventricle acting as one (common) electrode and asecond set of two electrodes on opposite sides of the left ventricleacting as the opposite (common) electrode. Alternatively, two of theelectrodes can be activated while the other two electrodes act as dummyelectrodes in that they would not be activated unless necessary.

At present, commercially available implantablecardioverter/defibrillators (ICD's) are capable of deliveringapproximately thirty to forty joules in order to defibrillate the heart.With respect to the present invention, it is preferred that theelectrodes 22 of the cardiac harness 20 of the present invention deliverdefibrillating shocks having less than thirty to forty joules. Thecommercially available ICD's can be modified to provide lower powerlevels to suit the present invention cardiac harness system withelectrodes delivering less than thirty to forty joules of power. As ageneral rule, one objective of the electrode configuration is to createa uniform current density distribution throughout the myocardium.Therefore, in addition to the number of electrodes used, their size,shape, and relative positions will also all have an impact on theinduced current density distribution. Thus, while one to four electrodesare preferred embodiments of the invention, five to eight electrodesalso are envisioned.

In keeping with the present invention, the cardiac harness and theassociated cardiac rhythm management device can be used not only forproviding a defibrillating shock, but also can be used as apacing/sensing device for treating the synchrony of both ventricles, forresynchronization, for biventricular pacing and for left ventricularpacing or right ventricular pacing. As shown in FIGS. 8A–8D, the heart10 is shown in cross-section exposing the right ventricle 11 and theleft ventricle 12. The cardiac harness 20 is mounted around the outersurface of the heart, preferably on the epicardial surface of the heart,and multiple electrodes are associated with the cardiac harness. Morespecifically, electrodes 32 are attached to the cardiac harness andpositioned around the circumference of the heart on opposite sides ofthe right and left ventricles. In the event that fibrillation shouldoccur, the electrodes will provide an electrical shock through themyocardium and the left and right ventricles in order to defibrillatethe heart. Also mounted on the cardiac harness, is a pacing/sensing lead40 that functions to monitor the heart and provide data to a pacemaker.If required, the pacemaker will provide pacing stimuli to synchronizethe ventricles, and/or provide left ventricular pacing, rightventricular pacing or biventricular pacing. Thus, for example, in FIG.8C, pairs of pacing/sensing leads 40 are positioned adjacent the leftand right ventricle free walls and can be used to provide pacing stimulito synchronize the ventricles, or provide left ventricular pacing, rightventricular pacing or biventriculator pacing. The use of proximal Yconnectors can simplify the transition to a post-generator such asOscor's, iLink-B15-10. The iLink-B15-10 can be used to link the rightand left ventricular free-wall pace/sense leads 40, as shown in 8D.

In another embodiment of the invention, as shown in FIGS. 9–14, cardiacharness 60 is similar to previously described cardiac harness 20. Withrespect to cardiac harness 60, it also includes panels 61 consisting ofundulating strands 62. In the disclosed embodiments, the undulatingstrands are continuous and extend through coils as will be described.The undulating strands act as spring elements 63 as with priorembodiments that will expand and contract along directional line 64. Thecardiac harness 60 includes a base or upper end 65 and an apex or lowerend 66. In order to add stability to the cardiac harness 60, and toassist in maintaining the spacing between the undulating strands 62,grip pads 67 are connected to adjacent strands, preferably at the apex68 of the springs. Alternatively, the grip pads 67 could be attachedfrom the apex of one spring element to the side 69 of a spring element,or the grip pad could be attached from the side of one spring to theside of an adjacent spring on an adjacent undulating strand. In furtherkeeping with the invention as shown in the FIGS. 9–14, in order to addstability and some mechanical stiffness to the cardiac harness 60, coils62 are interwoven with the undulating strands, which together define thepanels 61. The coils typically are formed of a coil of wire such asNitinol or similar material (stainless steel, MP35N), and are highlyflexible along their longitudinal length. The coils 72 have a coil apex73 and a coil base 74 to coincide with the harness base 65 and theharness apex 66. The coils can be injected with a non-conductingmaterial so that the undulating strands extend through gaps in the coilsand through the non-conducting material. The non-conducting materialalso fills in the gaps which will prevent the undulating strands fromtouching the coils so there is no metal-to-metal touching between theundulating strands and the coils. Preferably, the non-conductingmaterial is a dielectric material 77 that is formed of silicone rubberor equivalent material as previously described. Further, a dielectricmaterial 78 also covers the undulating strands in the event adefibrillating shock or pacing stimuli is delivered to the heart via anexternal defibrillator (e.g., transthoracic) or other means.

Importantly, coils 72 not only perform the function of being highlyflexible and provide the attachment means between the coils and theundulating strands, but they also provide structural columns or spinesthat assist in deploying the harness 60 over the epicardial surface ofthe heart. Thus, as shown for example in FIG. 12, the cardiac harness 60has been positioned over the heart and delivered by minimally invasivemeans, as will be described more fully herein. The coils 72, althoughhighly flexible along their longitudinal length, have sufficient columnstrength in order to push on the apex 73 of the coils so that the baseportion 74 of the coils and of the harness 65 slide over the apex of theheart and along the epicardial surface of the heart until the cardiacharness 60 is positioned over the heart, substantially as shown in FIG.12.

Referring to the embodiments shown in FIGS. 9 and 11, the cardiacharness 60 has multiple panels 61 and multiple coils 72. More or fewerpanels and coils can be used in order to achieve a desired result. Forexample, eight coils are shown in FIGS. 9 and 11, while fewer coils mayprovide a harness with greater flexibility since the undulating strands62 would be longer in the space between each coil. Further, the diameterof the coils can be varied in order to increase or decrease flexibilityand/or column strength in order to assist in the delivery of the harnessover the heart. The coils preferably have a round cross-sectional wirein the form of a tightly wound spiral or helix so that the cross-sectionof the coil is circular. However, the cross-sectional shape of the coilneed not be circular, but may be more advantageous if it were oval,rectangular, or another shape. Thus, if coils 72 had an oval shape,where the longer axis of the oval was parallel to the circumference ofthe heart, the coil would flex along its longitudinal axis and stillprovide substantial column strength to assist in delivery of the cardiacharness 60. Further, an oval-shaped coil would provide a lower profilefor minimally invasive delivery. The wire cross-section also need not beround/circular, but can consist of a flat ribbon having a rectangularshape for low profile delivery. The coils also can have differentshapes, for example they can be closed coils, open coils, laser-cutcoils, wire-wound coils, multi-filar coils, or the coil strandsthemselves can be coiled (i.e., coiled coils). The electrode need nothave a coil of wire, rather the electrode could be formed by azig-zag-shaped wire (not shown) extending along the electrode. Such adesign would be highly flexible and fatigue resistant yet still becapable of providing a defibrillating shock.

The cardiac harness embodiments 60 shown in FIGS. 9–12, can be folded asshown in FIGS. 13 and 14 and yet remain highly flexible for minimallyinvasive delivery. The coils 72 act as hinges or spines so that thecardiac harness can be folded along the longitudinal axis of the coils.The grip pads typically connecting adjacent undulating strands 62 havebeen omitted for clarity in these embodiments, however, they would beused as previously described.

In an alternative embodiment, similar to the embodiment shown in FIGS.9–12, the cardiac harness 60 includes both coils 72 and electrodes 32.In this embodiment, as with the previously described embodiments, aseries of undulating strands 22 extend between the coils and theelectrodes to form panels 21. In this embodiment, for example, the coilsand electrodes form hinge regions so that the panels can be folded alongthe longitudinal axis of the coils and electrodes for minimally invasivedelivery. Further, in this embodiment, there are two coils and fourelectrodes, with two of the electrodes positioned adjacent the rightventricle, with the remaining two electrodes being positioned adjacentthe left ventricle. The coils not only act as a hinge, but providecolumn strength as previously described so that the cardiac harness canbe delivered minimally invasively by delivery through, for example, theintercostal space between the ribs and then pushing the harness over theheart. Likewise, the electrodes provide column strength as well, yetremain flexible along their longitudinal axis, as do the coils.

Referring to FIGS. 15A–15D, the electrodes 32 or the coils 72 can bemounted on the inner surface (touching the heart) or outer surface (awayfrom the heart) of the cardiac harness. Thus, the cardiac harness 20includes continuous undulating strands 22 that extend circumferentiallyaround the heart without any interruptions. The undulating strands areinterconnected by any interconnecting means, including grip pads 27, aspreviously described. In this embodiment, electrodes 32 or coils 72, orboth, are mounted on an inner surface 80 or an outer surface 81 of thecardiac harness 20. A dielectric material 82 is molded around theelectrodes or coils and around the undulating strands in order toconnect the electrodes and coils to the cardiac harness. Alternatively,as shown in FIG. 15D, the electrodes 32 or coils 72 can be formed into afastening means by forming notches 83 into the electrode (or coil) andwhich are configured to receive portions of the undulating strand 22.The undulating strands 22 are spaced from the coils or electrodes sothat there is no overlapping/touching of metal. The notches 83 arefilled with a dielectric material, preferably silicone rubber, orsimilar material that insulates the undulating strands of the cardiacharness from the electrodes yet provides a secure attachment means sothat the electrodes or coils remain firmly attached to the undulatingstrands of the cardiac harness. Importantly, the electrodes 32 do nothave to be in contact with the epicardial surface of the heart in orderto deliver a defibrillating shock. Thus, the electrodes 32 can bemounted on the outer surface 81 of the cardiac harness, and not be inphysical contact with the epicardial surface of the heart, yet stilldeliver a defibrillating shock as previously described.

It is to be understood that several embodiments of cardiac harnesses canbe constructed and that such embodiments may have varyingconfigurations, sizes, flexibilities, etc. Such cardiac harnesses can beconstructed from many suitable materials including various metals,fabrics, plastics and braided filaments. Suitable materials also includesuperelastic materials and materials that exhibit shape memoryproperties. For example, a preferred embodiment cardiac harness isconstructed of Nitinol. Shape memory dielectric materials can also beemployed. Such shape memory dielectric materials can include shapememory polyurethanes or other dielectric materials such as thosecontaining oligo(e-caprolactone) dimethacrylate and/orpoly(e-caprolactone), which are available from mnemoScience.

In keeping with the invention, as shown in FIG. 16, the undulatingstrands 22 and 62 can be formed in many ways, including by a fixture 90.The fixture 90 has a number of stems 91 that are arranged in apre-selected pattern that will define the shape of the undulatingstrands 22 and 62. The position of the stems will define the shape ofthe undulating strands, and determine whether the previously disclosedapex of the springs is either in-phase or out-of-phase. The shape ofstems 91 will define the shape of the springs in terms of radius ofcurvature, or other shape, such as a keyhole shape, a U-shape, and thelike. The spacing between the stems will determine the pitch and theamplitude of the undulating strands which is a matter of choice.Preferably, in one exemplary embodiment, a Nitinol wire 92 or othersuperelastic or shape memory wire having a 0.012 inch diameter, is wovenbetween stems 91 in order to form the undulating strands. Other wirediameters can be used to suit a particular need and can range from about0.007 inch to about 0.020 inch diameter. Other wire cross-section shapesare envisioned to be used with fixture 90, particularly a flatrectangular-shaped wire and an oval-shaped wire. The Nitinol wire isthen heat set to impart the shape memory feature. Any free ends can beconnected together by laser bonding, laser welding, or other type ofsimilar connection consistent with the use of Nitinol, or the ends mayremain free and be encapsulated in a dielectric material to keep thematraumatic, depending upon the design.

Again referring to FIG. 16, after the Nitinol wire is heat set to impartthe shape memory feature, the wire is jacketed with NuSil siliconetubing (Helix Medical) having 0.029 inch outside diameter by 0.012 inchinside diameter. Thereafter, the jacketed Nitinol wire is placed inmolds for transfer of liquid silicone rubber which will insulate theNitinol wire from any electrical shock from any electrodes associatedwith the cardiac harness, or any other device providing a defibrillatingshock to the heart. The dimensions of the silicone tubing will of coursevary for different wire dimensions.

In another embodiment of the invention, shown in FIG. 17, cardiacharness 100 includes multiple panels 101 similar to those previouslydescribed. Further, undulating strands 102 form the panels and havemultiple spring elements 103 that expand and contract along directionalline 104, also as previously described for other embodiments. In thecardiac harness 100 shown in FIG. 17, the amplitude of the springelements is relatively smaller than in other embodiments, and the pitchis higher, meaning there are more spring elements per unit of lengthrelative to other embodiments. Thus, the cardiac harness 100 shouldgenerate higher bending forces as the heart expands and contracts duringthe diastolic and systolic cycles. In other words, the spring elements103 of cardiac harness 100 will resist expansion, thereby impartinghigher compressive forces on the wall of the heart during the diastolicfunction and will release these higher bending forces during thesystolic function as the heart contracts. It may be important to provideundulating strands 102 that alternate in amplitude and pitch within apanel, starting at the base of the harness and extending toward theapex. For example, the pitch and amplitude of an undulating strandcloser to the base or the harness may be configured to impart highercompressive forces on the epicardial surface of the heart than theundulating strands closer to the apex or the lower part of the harness.It also may be desirable to alternate the amplitude and pitch of thespring elements from one undulating strand to the next. Further, wheremultiple panels are provided, it may be advantageous to provide oneamplitude and pitch of the spring elements of the undulating strands ofone panel, and a different amplitude and pitch of the spring elements ofthe undulating strands of an adjacent panel. The FIG. 17 embodiment canbe configured with electrodes as previously described in otherembodiments, or with coils, both of which assist with the delivery ofthe cardiac harness by providing column support to the harness.

The cardiac harness of the present invention, having either electrodesor coils, can be formed using injection molding techniques as shown inFIGS. 18A–18C and 19A–19C. The molds in FIGS. 18A–18C are substantiallythe same as the molds shown in FIGS. 19A–19C, with the exception of theundulating pattern grooves that receive the undulating strandspreviously described. In referring to FIG. 18A, bottom mold 110 includesa pattern for receiving the cardiac harness and a coil or an electrode.For illustration purposes, FIG. 18B shows top mold 111 and FIG. 18Cshows end view mold 112. The top mold mates with the bottom mold. As canbe seen, the cardiac harness undulating strands will fit in undulatingstrand groove 113, which extend into coil groove 114. The previouslydescribed electrodes or coils fit into coil grooves 114. Injection port115 is positioned midway along the mold fixtures, however, more than oneinjection port can be used to insure that the flow of polymer is uniformand consistent. Preferably, silicone rubber is injected into the moldsso that the silicone rubber flows over the undulating strands and theelectrodes or the coils. When the cardiac harness assembly is taken outof the mold, the undulating strands will be attached to the electrodesor the coils by the silicone rubber according to the pattern shown.Other patterns may be desired and the molds are easily altered toprovide any pattern that ensures a secure attachment between theundulating strands and the electrodes or the coils. Importantly, themolds of FIGS. 18 and 19 can be used to inject the dielectric materialor silicone rubber inside the coils and, if necessary, between the gapsin the coils in order to insure that the coils and the undulatingstrands are insulated from each other. The silicone rubber fills theinside of the coils, extrudes through the gaps in the coils, and forms askin on the inner and outer surface of the coil. This skin isselectively removed (as will be described) to expose portions of theelectrode coils so that they can conduct current as described. Further,it is desired that the coils and the undulating strands do not overlapor touch in order to reduce any frictional engagement between themetallic coils and the metallic undulating strands. In order to increasethe frictional engagement between the cardiac harness and the epicardialsurface of the heart, small projections (not shown) can be molded alongthe surface of the coils that will contact the epicardial surface. Aspreviously described with respect to the grip pads, these smallprojections, preferably formed of silicone rubber, will engage theepicardial surface of the heart and increase the frictional engagementbetween the coils and the surface of the heart in order to secure theharness to the heart without the use of sutures, clips, or othermechanical attachment means.

In further keeping with the invention, as shown in FIGS. 20–23, aportion of a lead having an electrode 120 is shown in the form of aconductive coil 121. The coil can be formed of any suitable wire that isconductive so that an electrical shock can be transmitted through theelectrode and through the myocardium of the heart. In this embodiment,the coil wire is wrapped around a dielectric material 122 in a helicalconfiguration, however, a spiral wrap or other configuration is possibleas long as the coil has superior fatigue resistance and longitudinalflexibility. Importantly, conductive coils 121 have high fatigueresistance which is necessary since the coil is on or near the surfaceof the beating heart so that the coil is constantly flexing along itslongitudinal length in response to heart expansion and contraction. Thecross-section of the wire preferably is round or circular, however, italso can be oval shaped or flat (rectangular) in order to reduce theprofile of the electrode for minimally invasive delivery. A circular,oval or flat wire will have a relatively high fatigue resistance as wellas a relatively low profile for delivery purposes. Also, a flat wirecoil is highly flexible along the longitudinal axis and it has arelatively high surface area for delivering an electrical shock. Theelectrode 120 has a first surface 123 and a second surface 124. Thefirst surface 123 will be proximate the epicardial surface of the heart,or other portions of the heart, while the second surface will beopposite the first surface and away from the epicardial surface of theheart. A conductive wire (not shown) extends through the dielectricmaterial 122 and attaches to the coil wire 121 at one or more locationsalong the coil or coils, and the conductive wire is connected to a powersource (e.g., an ICD) at its other end. As shown in FIG. 22, thecross-section of the electrode 120 can be circular, or as shown in FIG.23, can be oval for reduced profile for minimally invasive delivery.Other cross-sectional shapes for electrode 120 are available dependingupon the particular need. All of these cross-sectional shapes will haverelatively high fatigue resistance. As shown in FIGS. 22 and 23,multiple lumens 125 can be provided to carry one or more conductivewires from the electrode to the power source (pulse generator, ICD,CRT-D, pacemaker, etc.). The lumens also can carry sensing wires thattransmit data from a sensor on or in the heart to a pacemaker so thatthe heart can be monitored. Further, the lumens 125 can be used forother purposes such as drug delivery (therapeutic drugs, steroids,etc.), dye injection for visability under fluoroscopy, carrying a guidewire (not shown) or a stylet to facilitate delivery of the electrodesand the harness, or for other purposes. The lumens 125 can be used tocarry a guide wire (not shown) or a stylet in such a way that the columnstiffness of the coil is increased by the guide wire or stylet, or in amanner that will vary the column stiffness as required. By varying thecolumn stiffness of the coils with a guide wire or a stylet in lumens125, the ability to push the cardiac harness over the heart (as will bedescribed) will be enhanced. The guide wires or stylets also can beused, to some extent, to steer the coils and hence the cardiac harnessduring delivery and implantation over the heart. The guide wire orstylet in lumens 125 can be removed after the cardiac harness isimplanted so that the coils (electrodes) become more flexible andatraumatic.

In keeping with the invention, as shown in FIGS. 20–23, the electrode120 not only provides an electrical conduit for use in defibrillation,but also has sufficient column strength when attached to the cardiacharness to assist in the delivery of the harness by minimally invasivemeans. As will be further described, the coils 121 provide a highlyflexible electrode along its longitudinal length, and also provide asubstantial amount of column strength when coupled with a cardiacharness to assist in the delivery of the harness.

In further keeping with the invention of FIGS. 20–23, a dielectricmaterial such as silicone rubber 126 can be used to coat electrodes 120.During the molding process (previously described), when the electrode120 is attached to the cardiac harness, silicone rubber 126 will coatthe entire electrode 120. Soda blasting (or other known material removalprocess) can be used to remove portions of the silicone rubber skin fromthe coils 121 in order to expose first surface 123 and second surface124 (or portions of those surfaces) so that the bare metal coil isexposed to the epicardial surface of the heart. Preferably, the siliconerubber is removed from both the first surface and the second surface,however, it also may be advantageous to remove the silicone rubber fromonly the first surface, which is proximate to or in contact with theepicardial surface of the heart. The electrode 120 has a surface area128 which essentially includes all of the bare metal surface area thatis exposed and that will deliver a shock. The amount of surface area perelectrode can vary greatly depending upon a particular application,however, surface areas in the range from about 50 mm² to about 600 mm²are typical. While it is possible to remove the silicone rubber fromonly the second surface (facing away from the heart), and leaving thefirst surface coated with silicone rubber, an electrical shock can stillbe delivered from the bare metal second surface, however, the electricalshock delivered may not be as efficient as with other embodiments. Whilethe dimensions of the electrodes can vary widely due to the variationsin the size of the heart to be treated in conjunction with the size ofthe cardiac harness, generally the length of the electrode ranges fromabout 2 cm to about 16 cm. The coil 121 has a length in the range ofabout 1 cm to about 12 cm. Commercially available leads having one ormore electrodes are available from several sources and may be used withthe cardiac harness of the present invention. Commercially availableleads with one or more electrodes is available from Guidant Corporation(St. Paul, Minn.), St. Jude Medical (Minneapolis, Minn.) and MedtronicCorporation (Minneapolis, Minn.). Further examples of commerciallyavailable cardiac rhythm management devices, including defibrillationand pacing systems available for use in combination with the cardiacharness of the present invention (possibly with some modification)include, the CONTAK CD®, the INSIGNIA® Plus pacemaker and FLEXTREND®leads, and the VITALITY™ AVT® ICD and ENDOTAK RELIANCE® defibrillationleads, all available from Guidant Corporation (St. Paul, Minn.), and theInSync System available from Medtronic Corporation (Minneapolis, Minn.).

In an alternative embodiment, as shown in FIG. 24, the conductive coils121 need not be continuous along the length of the electrode 120, butcan be spatially isolated or staggered along the electrode. For example,multiple coil sections 127, similar to the coil 121 shown in FIG. 20,can be spaced along the electrode with each coil section being attachedto the conductive wire so it receives electrical current from the powersource. The coil sections can be from about 0.5 cm to about 2.0 cm longand be spaced from about 0.5 cm to about 4 cm apart along the electrode.The dimensions used herein are by way of example only and can vary tosuit a particular application.

When removing portions of the silicone rubber from the electrode 120using soda blasting or a similar technique, it may be desirable to leaveportions of the electrode masked or insulated so that the masked portionis non-conductive. By masking portions of two electrodes positioned, forexample, on opposite sides of the left ventricle, it is possible tovector a shock at a desirable angle through the myocardium andventricle. The shock will travel from the bare metal (unmasked) portionof one electrode through the myocardium and the ventricle to the baremetal (unmasked) portion of the opposing electrode at a vector angledetermined by the position of the masking on the electrodes.

The cardiac rhythm management devices associated with the presentinvention are implantable devices that provide electrical stimulation toselected chambers of the heart in order to treat disorders of cardiacrhythm and can include pacemakers and implantablecardioverter/defibrillators and/or cardiac resynchronization therapydevices (CRT-D). A pacemaker is a cardiac rhythm management device whichpaces the heart with timed pacing pulses. As previously described,common conditions for which pacemakers are used is in the treatment ofbradycardia (ventricular rate is too slow) and tachycardia (cardiacrhythms are too fast). As used herein, a pacemaker is any cardiac rhythmmanagement device with a pacing functionality, regardless of any otherfunctions it may perform such as the delivery of cardioversion ordefibrillation shocks to terminate atrial or ventricular fibrillation.An important feature of the present invention is to provide a cardiacharness having the capability of providing a pacing function in order totreat the synchrony of both ventricles. To accomplish the objective, apacemaker with associated leads and electrodes are associated with andincorporated into the cardiac harness of the present invention. Thepacing/sensing electrodes, alone or in combination with defibrillatingelectrodes, provide treatment to synchronize the ventricles and improvecardiac function.

In keeping with the invention, a pacemaker and a pacing/sensingelectrode are incorporated into the design of the cardiac harness. Asshown in FIGS. 25A and 25B, a lead (not shown) having a defibrillatorelectrode 130 at its distal end, shown in partial section, not onlyincorporates wire coils 131 used to deliver a defibrillating electricalshock to the epicardial surface of the heart, but also incorporates apacing/sensing electrode 132. The defibrillator electrode 130 can beattached to any cardiac harness embodiment previously described herein.In this embodiment, a non-penetrating pacing/sensing electrode 132 iscombined with the defibrillating electrode 130 in order to provide datarelating to heart function. More specifically, the pacing/sensingelectrode 132 does not penetrate the myocardium in this embodiment,however, it may be beneficial in other embodiments for the pacing orsensing electrode to penetrate the myocardium. One advantage of anon-penetrating pacing/sensing electrode is that there is no danger ofpuncturing a coronary artery or causing further trauma to the epicardiumor myocardium. It is also easier to design since there is no requirementof a penetration mechanism (barb or screw) on the pacing/sensingelectrode. The pacing/sensing electrode 132 is in direct contact withthe epicardial surface of the heart and will provide data via lead wire133 to the pulse generator (pacemaker), which will interpret the dataand provide any pacing function necessary to achieve, for example,ventricular resynchronization therapy, left ventricular pacing, rightventricular pacing, synchrony of both ventricles, and/or biventricularpacing. As shown in FIG. 25B, the pacing/sensing electrode 132 isincorporated into a portion of a cardiac harness 134, and moreparticularly the undulating strands 135 are attached by dielectricmaterial 136 to the pacing/sensing electrode. As can be seen in FIGS.25A and 25B, the wire coils 131 of the defibrillating electrode 130 arewrapped around the dielectric material 136, and the dielectric materialinsulates the pacing/sensing electrode 132 from both the wire coils 131and from the undulating strands 135 of the cardiac harness. Multiplepacing/sensing electrodes 132 can be incorporated along defibrillatingelectrode 130, and multiple pacing and sensing electrodes can beincorporated on other electrodes associated with the cardiac harness.

In one of the preferred embodiments, multi-site pacing (as previouslyshown in FIGS. 8A–8D) using pacing/sensing electrodes 132 enablesresynchronization therapy in order to treat the synchrony of bothventricles. Multi-site pacing allows the positioning of thepacing/sensing electrodes to provide bi-ventricular pacing or rightventricular pacing, left ventricular pacing, depending upon thepatient's needs.

In another embodiment, shown in FIGS. 26A–26C, a defibrillatingelectrode is combined with pacing/sensing electrodes, for attachment toany of the cardiac harness embodiments disclosed herein. In thisembodiment, the defibrillating electrode 130 is formed of wire coils 131wrapped in a helical manner. The helical wire can be a wound wire havinga single strand or a quadrafilar wire having four wires bundled togetherto form the coil. The wire coils 131 are wrapped around dielectricmaterial 136 in a manner similar to that described for the embodimentsin FIGS. 25A and 25B. In this embodiment, the pacing/sensing electrode132 is in the form of a single ring for unipolar operation, and tworings for bi-polar operation. The pacing/sensing electrode rings 132 aremounted coaxially with the defibrillating electrode wire coils 131, andthe conducting wires from the wire coils and the pacing/sensing ringelectrode are shown extending through the dielectric material 136 andbeing insulated from each other. The conducting wires from thedefibrillating electrode 130 and from the pacing/sensing ring electrodes132 can be bundled into a common lead wire 133 which extends to thepulse generator (an ICD, CRT-D, and/or a pacemaker). As can be seen inFIGS. 26A–26C, the pacing/sensing electrode rings 132 have a diameterthat is somewhat larger than the defibrillator electrode coils 131 inorder to insure preferential contact by the electrode rings against theepicardial surface of the heart. Preferably, several pairs ofpacing/sensing electrode rings (bipolar) would be positioned on thecardiac harness and be positioned to come into contact with, forexample, the left ventricle free wall. Multi-site pacing allows thepacing/sensing electrode rings 132 to be used for both pacing andresynchronization concurrently. Further, the pacing/sensing electroderings 132 also can be used in the absence of defibrillating electrodes130. The prior disclosure relating to molding of the cardiac harness tothe defibrillator electrode applies equally as well to thepacing/sensing electrode rings. The wire coil 131 and the pacing/sensingelectrode rings 32 can be fabricated in several ways including by lasercutting stainless steel tubing or using highly conductive materials inwire form, such as biocompatible platinum wire. As previously disclosed,the wire coils 131 can be quadrafilar wire (platinum) for improvedflexibility and conformability to the epicardial surface of the heartand be biocompatible. The surface of the pacing/sensing electrodes canvary greatly depending upon the application. As an example, in oneembodiment, the surface area of the pacing/sensing electrodes are in therange from about 2 mm² to about 12 mm², however, this range can varysubstantially. While the disclosed embodiments show the pacing/sensingelectrodes combined with the defibrillating electrodes, thepacing/sensing electrodes can be formed separately and mounted on thecardiac harness with or without defibrillating electrodes.

The defibrillating electrode 130 as disclosed herein, can be used withcommercially available pacing/sensing electrodes and leads. For example,Oscor (Model HT 52PB) endocardial/passive fixation leads can beintegrated with the defibrillator electrode 130 by molding the leadsinto the fibrillator electrode using the same molds previously disclosedherein.

The foregoing disclosed invention incorporating cardiac rhythmmanagement devices into the cardiac harness combines several treatmentmodalities that are particularly beneficial to patients suffering fromcongestive heart failure. The cardiac harness provides a compressiveforce on the heart thereby relieving wall stress, and improving cardiacfunction. The defibrillating and pacing/sensing electrodes associatedwith the cardiac harness, along with ICD's and pacemakers, providenumerous treatment options to correct for any number of maladiesassociated with congestive heart failure. In addition to thedefibrillation function previously described, the cardiac rhythm devicescan provide electrical pacing stimulation to one or more of the heartchambers to improve the coordination of atrial and/or ventricularcontractions, which is referred to as resynchronization therapy. Cardiacresynchronization therapy is pacing stimulation applied to one or moreheart chambers, typically the ventricles, in a manner that restores ormaintains synchronized bilateral contractions of the atria and/orventricles thereby improving pumping efficiency. Resynchronizationpacing may involve pacing both ventricles in accordance with asynchronized pacing mode. For example, pacing at more than one site(multi-site pacing) at various sites on the epicardial surface of theheart to desynchronize the contraction sequence of a ventricle (orventricles) may be therapeutic in patients with hypertrophic obstructivecardiomyopathy, where creating asynchronous contractions with multi-sitepacing reduces the abnormal hyper-contractile function of the ventricle.Further, resynchronization therapy may be implemented by addingsynchronized pacing to the bradycardia pacing mode where paces aredelivered to one or more synchronized pacing sites in a defined timerelation to one or more sensing and pacing events. An example ofsynchronized chamber-only pacing is left ventricle only synchronizedpacing where the rate in synchronized chambers are the right and leftventricles respectively. Left-ventricle-only pacing may be advantageouswhere the conduction velocities within the ventricles are such thatpacing only the left ventricle results in a more coordinated contractionby the ventricles than by conventional right ventricle pacing or byventricular pacing. Further, synchronized pacing may be applied tomultiple sites of a single chamber, such as the left ventricle, theright ventricle, or both ventricles. The pacemakers associated with thepresent invention are typically implanted subcutaneously on a patient'schest and have leads threaded to the pacing/electrodes as previouslydescribed in order to connect the pacemaker to the electrodes forsensing and pacing. The pacemakers sense intrinsic cardiac electricalactivity through the electrodes disposed on the surface of the heart.Pacemakers are well known in the art and any commercially availablepacemaker or combination defibrillator/pacemaker can be used inaccordance with the present invention.

The cardiac harness and the associated cardiac rhythm management devicesystem of the present invention can be designed to provide leftventricular pacing. In left heart pacing, there is an initial detectionof a spontaneous signal, and upon sensing the mechanical contraction ofthe right and left ventricles. In a heart with normal right heartfunction, the right mechanical atrio-ventricular delay is monitored toprovide the timing between the initial sensing of right atrialactivation (known as the P-wave) and right ventricular mechanicalcontraction. The left heart is controlled to provide pacing whichresults in left ventricular mechanical contraction in a desired timerelation to the right mechanical contraction, e.g., either simultaneousor just preceding the right mechanical contraction. Cardiac output ismonitored by impedence measurements and left ventricular pacing is timedto maximize cardiac output. The proper positioning of the pacing/sensingelectrodes disclosed herein provides the necessary sensing functions andthe resulting pacing therapy associated with left ventricular pacing.

An important feature of the present invention is the minimally invasivedelivery of the cardiac harness and the cardiac rhythm management devicesystem which will be described immediately below.

Delivery of the cardiac harness 20,60, and 100 and associated electrodesand leads can be accomplished through conventional cardio-thoracicsurgical techniques such as through a median sternotomy. In such aprocedure, an incision is made in the pericardial sac and the cardiacharness can be advanced over the apex of the heart and along theepicardial surface of the heart simply by pushing it on by hand. Theintact pericardium is over the harness and helps to hold it in place.The previously described grip pads and the compressive force of thecardiac harness on the heart provide sufficient attachment means of thecardiac harness to the epicardial surface so that sutures, clips orstaples are unnecessary. Other procedures to gain access to theepicardial surface of the heart include making a slit in the pericardiumand leaving it open, making a slit and later closing it, or making asmall incision in the pericardium.

Preferably, however, the cardiac harness and associated electrodes andleads may be delivered through minimally invasive surgical access to thethoracic cavity, as illustrated in FIGS. 27–36, and more specifically asshown in FIG. 30. A delivery device 140 may be delivered into thethoracic cavity 141 between the patient's ribs to gain direct access tothe heart 10. Preferably, such a minimally invasive procedure isaccomplished on a beating heart, without the use of cardio-pulmonarybypass. Access to the heart can be created with conventional surgicalapproaches. For example, the pericardium may be opened completely or asmall incision can be made in the pericardium (pericardiotomy) to allowthe delivery system 140 access to the heart. The delivery system of thedisclosed embodiments comprises several components as shown in FIGS.27–36. As shown in FIG. 27, an introducer tube 142 is configured for lowprofile access through a patient's ribs. A number of fingers 143 areflexible and have a delivery diameter 144 as shown in FIG. 27, and anexpanded diameter 145 as shown in FIG. 29. The delivery diameter issmaller than the expanded diameter. An elastic band 146 expands aroundthe distal end 147 of the fingers and prevents the fingers fromoverexpanding during delivery of the cardiac harness. The distal end ofthe fingers is the part of the delivery device 140 that is insertedthrough the patient's ribs to gain direct access to the heart.

The delivery device 140 also includes a dilator tube 150 that has adistal end 151 and a proximal end 152. The cardiac harness 20,60,100 iscollapsed to a low profile configuration and inserted into the distalend of the dilator tube, as shown in FIG. 28. The dilator tube has anoutside diameter that is slightly smaller than the inside diameter ofthe introducer tube 142. As will be discussed more fully herein, thedistal end 151 of the dilator tube is inserted into the proximal end 147of the introducer tube in close sliding engagement and in a slightfrictional engagement. The slidable engagement between the dilator tubeand the introducer tube should be with some mild resistance, however,there should be unrestricted slidable movement between the two tubes.The distal end 151 of the dilator tube will expand the fingers 143 ofthe introducer tube 142 as the dilator tube is pushed distally into theintroducer tube as shown in FIG. 29. In the embodiments shown in FIGS.27–36, the cardiac harness 20,60,100 is equipped with leads (previouslydescribed) having electrodes for use in defibrillation or pacingfunctions.

As shown in FIG. 31, the delivery system 140 also includes a releasablesuction device, such as suction cup 156 at the distal end of thedelivery device. The negative pressure suction cup 156 is used to holdthe apex of the heart 10. Negative pressure can be applied to thesuction cup using a syringe or other vacuum device commonly known in theart. A negative pressure lock can be achieved by a one-way valvestop-cock or a tubing clamp, also known in the art. The suction cup 156is formed of a biocompatible material and is preferably stiff enough toprevent any negative pressure loss through the heart while manipulatingthe heart and sliding the cardiac harness 20,60,100 onto the heart.Further, the suction cup 156 can be used to lift and maneuver the heart10 to facilitate advancement of the harness or to allow visualizationand surgical manipulation of the posterior side of the heart. Thesuction cup has enough negative pressure to allow a slight pulling inthe proximal direction away from the apex of the heart to somewhatelongate the heart (e.g., into a bullet shape) during delivery tofacilitate advancing the cardiac harness over the apex and onto the baseportion of the heart. After the suction cup 156 is attached to the apexof the heart and a negative pressure is drawn, the cardiac harness,which has been releasably mounted in the distal end 151 of the dilatortube 150, can be advanced distally over the heart, as will be describedmore fully herein.

As shown in FIG. 30, the delivery device 140, and more specificallyintroducer tube 142, has been advanced through the intercostal spacebetween the patient's ribs during insertion of the introducer tube, thefingers 143 are in their delivery diameter 144, which is a low profilefor ease of access through the small port made through the patient'sribs. Thereafter, the dilator tube 150, with the cardiac harness20,60,100 mounted therein, is advanced distally through the introducertube so that the fingers 143 are expanded until they achieve theirexpanded diameter 145. The suction cup 156 can be attached to the apex13 of the heart 10 either before or after the dilator tube is advancedto spread the fingers 143 of the introducer tube 142. Preferably, thedilator tube has already expanded the fingers on the introducer tube sothat there is a larger opening for the suction cup as it is advancedthrough the inside of a dilator tube, out of the distal end of theintroducer tube, and placed in contact with the apex of the heart.Thereafter, a negative pressure is drawn allowing the suction cup tosecurely attach to the apex of the heart. Visualizing equipment that iscommonly known in the art may be used to assist in positioning thesuction cup to the apex. For example, fluoroscopy, magnetic resonanceimaging (MRI), dye injection to enhance fluoroscopy, andechocardiography, and intracardiac, transesophageal, or transthoracicecho, all can be used to enhance positioning and in attaching thesuction cup to the apex of the heart. After negative pressure is drawnand the suction cup is securely attached (releasably) to the apex of theheart, the heart can then be maneuvered somewhat by pulling on thetubing 157 attached to the suction cup, or by manipulating theintroducer tube 142, the dilator tube 150, both in conjunction with thesuction cup. As previously described, it may be advantageous to pull onthe tubing 157 to allow the suction cup to pull on the apex of the heartand elongate the heart somewhat in order to facilitate sliding theharness over the epicardium.

As more clearly shown in FIGS. 32–36, the cardiac harness 20,60,100 isadvanced distally out of the dilator tube and over the suction cup 156.The suction cup is tapered so that the distal end of the harness slidesover the narrow portion of the taper (the proximal end of the suctioncup 158). The suction cup becomes wider at its distal end where it isattached to the apex of the heart, and the cardiac harness continues toslide and expand over the suction cup as it is advanced distally. As thecardiac harness continues to be advanced distally, it slides over theapex of the heart and continues to expand as it is pushed out of thedilator tube and along the epicardial surface of the heart. Since theharness and the electrodes 32,120,130 are coated with the previouslydescribed dielectric material, preferably silicone rubber, the cardiacharness should slide easily over the epicardial surface of the heart.The silicone rubber offers little resistance and the epicardial surfaceof the heart has sufficient fluid to allow the harness to easily slideover the wet surface of the heart. The pericardium previously has beencut so that the cardiac harness is sliding over the epicardial surfaceof the heart with the pericardium over the cardiac harness to help holdit onto the surface of the heart. As shown in FIGS. 35 and 36, thecardiac harness 20,60,100 has been completely advanced out of thedilator tube so that the harness covers at least a portion of the heart10. The suction cup 156 has been withdrawn, and the introducer tube 142and dilator tube 150 also have been withdrawn proximally from thepatient. Prior to removing the introducer tube, a power source 170 (suchas an ICD, CRT-D, and/or pacemaker) can be implanted by conventionalmeans. The electrodes will be attached to the pulse generator to providea defibrillating shock or pacing functions as previously described.

In the embodiments shown in FIGS. 27–36, the cardiac harness 20,60,100was advanced through the dilator tube by pushing on the proximal end ofthe electrodes 32,120,130, on the lead wires 31,133, and on the proximalend (apex 26) of the cardiac harness. Even though the electrodes aredesigned to be atraumatic and longitudinally flexible, the electrodeshave sufficient column strength so that pushing on the proximal ends ofthe electrodes assists in pushing the cardiac harness out of the dilatortube and over the epicardial surface of the heart. In one embodiment,advancement of the cardiac harness is accomplished by hand, by thephysician simply pushing on the electrodes and the leads to advance thecardiac harness out of the dilator tube to slide onto the epicardialsurface of the heart.

As shown in the embodiments of FIGS. 27–36, the delivery device 140, andmore specifically introducer tube 142 and dilator tube 150, have acircular cross-section. It may be preferable, however, to chose othercross-sectional shapes, such as an oval cross-sectional shape for thedelivery device. An oval delivery device may be more easily insertedthrough the intercostal space between the patient's ribs for a lowprofile delivery. Further, as the cardiac harness 20,60,100 is advancedout of a delivery device 140 having an oval cross-section, the harnessdistal end will quickly form into a more circular shape in order toassume the configuration of the epicardial surface of the heart as it isadvanced distally over the heart.

In the embodiments shown in FIGS. 35 and 36, the cardiac harness20,60,100 remains firmly attached to the epicardial surface of the heartwithout the need for any further attachment means, such as sutures,clips, adhesives, or staples. Further, the pericardial sac helps toenclose the harness to prevent it from shifting or sliding on theepicardial surface of the heart.

Importantly, during delivery of the cardiac harness 20,60,100, theharness itself, the electrodes 32,120,130, as well as leads 31 and 132have sufficient column strength in order for the physician to push fromthe proximal end of the harness to advance it distally through thedilator tube 150. While the entire cardiac harness assembly is flexible,there is sufficient column strength, especially in the electrodes, toeasily slide the cardiac harness over the epicardial surface of theheart in the manner described.

In an alternative embodiment, if the cardiac harness 20,60,100 includescoils 72, as opposed to the electrodes and leads, the harness can bedelivered in the same manner as previously described with respect toFIGS. 27–36. The coils have sufficient column strength to permit thephysician to push on the proximal end of the coils to advance thecardiac harness distally to slide over the apex of the heart and ontothe epicardial surface.

In another embodiment, delivery of the cardiac harness 20,60,100 can beby mechanical means as opposed to the hand delivery previouslydescribed. As shown in FIGS. 37–42, delivery system 180 includes anintroducer tube 181 that functions the same as introducer tube 142.Also, a dilator tube 182, which is sized for slidable movement withinthe introducer tube, also functions the same as the previously describeddilator tube 150. An ejection tube 183 is sized for slidable movementwithin the dilator tube, that is, the outer diameter of the ejectiontube is slightly smaller than the inner diameter of the dilator tube. Asshown in FIGS. 40 and 41, the ejection tube has a distal end 184 and aproximal end 185, wherein the distal end of the ejection tube has aplate that fills the entire inner diameter of the ejection tube. Theplate has a number of lumens 187 for receiving leads 31,132 and forreceiving the suction cup 156 and associated tubing 157. Thus, lumens188 are sized for receiving leads 31,132 therethrough, while lumen 189is sized for receiving suction cup 156 and the associated tubing 157.The number of lumens 188 in plate 186 will be defined by the number ofleads 31,132 associated with the cardiac harness 20,60,100. Thus, asshown in FIG. 40, there are four lumens 188 for receiving four leadstherethrough, and one lumen 189 for receiving the suction cup 156 andtubing 157 therethrough. The leads and the tubing 157 extend proximallyout the proximal end 185 of the ejection tube. As shown in FIG. 42, thesuction cup and cardiac harness are on the left side of the schematic,and the ejection tube 183 is on the right hand side of the schematic.For clarity, the dilator tube and the introducer tube have been omitted,however, in practice the cardiac harness would be mounted in the dilatortube, and the dilator tube would extend into the introducer tube, whilethe ejection tube would extend into the dilator tube. As can be seen inFIG. 42, the leads 31,132 extend through lumens 188, while the tubing157 associated with the suction cup extends through lumen 189. Thetubing and the leads extend proximally out of the proximal end of theejection tube, and extend out of the patient during delivery of theharness. As previously described, after the introducer is positionedthrough the rib cage, and the apex of the heart is acquired by thesuction cup, the harness can be advanced out of the dilator by advancingthe ejection tube 183 in a distal direction toward the apex of theheart. The leads, the cardiac harness and electrodes all providesufficient column strength to allow the plate 186 to impart a pushingforce against the cardiac harness to advance it distally over the heartas previously described. After the cardiac harness is pushed over theepicardial surface of the heart, the ejection tube can be withdrawnproximally so that the tubing 157 and the leads 31,132 slide throughlumens 189,188 respectively. The ejection tube 183 continues to bewithdrawn proximally so that the proximal end of the leads and theproximal end of tubing 157 are pulled through the distal end 184 of theejection tube so that the ejection tube is clear of the leads and thetubing.

As with the previous embodiment, suitable materials for the deliverysystem 140,180 can include the class of polymers typically used andapproved for biocompatible use within the body. Preferably, the tubingassociated with delivery systems 140 and 180 are rigid, however, theycan be formed of a more flexible material. Further, the delivery systems140,180 can be curved rather than straight, or can have a flexible jointin order to more appropriately maneuver the cardiac harness 20,60,100over the epicardial surface of the heart during delivery. Further, thetubing associated with delivery systems 140,180 can be coated with alubricious material to facilitate relative movement between the tubes.Lubricious materials commonly known in the art such as Teflon™ can beused to enhance slidable movement between the tubes.

Delivery and implantation of an ICD, CRT-D, pacemaker, leads, and anyother device associated with the cardiac rhythm management devices canbe performed by means well known in the art. Preferably, theICD/CRT-D/pacemaker, are delivered through the same minimally invasiveaccess site as the cardiac harness, electrodes, and leads. The leads arethen connected to the ICD/CRT-D/pacemaker in a known manner. In oneembodiment of the invention, the ICD or CRT-D or pacemaker (orcombination device) is implanted in a known manner in the abdominal areaand then the leads are connected. Since the leads extend from the apicalends of the electrodes (on the cardiac harness) the leads are wellpositioned to attach to the power source in the abdominal area.

It may be desired to reduce the likelihood of the development offibrotic tissue over the cardiac harness so that the elastic propertiesof the harness are not compromised. Also, as fibrotic tissue forms overthe cardiac harness and electrodes over time, it may become necessary toincrease the power of the pacing stimuli. As fibrotic tissue increases,the right and left ventricular thresholds may increase, commonlyreferred to as “exit block.” When exit block is detected, the pacingtherapy may have to be adjusted. Certain drugs such as steriods, havebeen found to inhibit cell growth leading to scar tissue or fibrotictissue growth. Examples of therapeutic drugs or pharmacologic compoundsthat may be loaded onto the cardiac harness or into a polymeric coatingon the harness, on a polymeric sleeve, on individual undulating strandson the harness, or infused through the lumens in the electrodes anddelivered to the epicardial surface of the heart include steroids,taxol, aspirin, prostaglandins, and the like. Various therapeutic agentssuch as antithrombogenic or antiproliferative drugs are used to furthercontrol scar tissue formation. Examples of therapeutic agents or drugsthat are suitable for use in accordance with the present inventioninclude 17-beta estradiol, sirolimus, everolimus, actinomycin D (ActD),taxol, paclitaxel, or derivatives and analogs thereof. Examples ofagents include other antiproliferative substances as well asantineoplastic, antiinflammatory, antiplatelet, anticoagulant,antifibrin, antithrombin, antimitotic, antibiotic, and antioxidantsubstances. Examples of antineoplastics include taxol (paclitaxel anddocetaxel). Further examples of therapeutic drugs or agents includeantiplatelets, anticoagulants, antifibrins, antinflammatories,antithrombins, and antiproliferatives. Examples of antiplatelets,anticoagulants, antifibrins, and antithrombins include, but are notlimited to, sodium heparin, low molecular weight heparin, hirudin,argatroban, forskolin, vapiprost, prostacyclin and prostacyclin analogs,dextran, D-phe-pro-arg-chloromethylketone (synthetic antithrombin),dipyridamole, glycoprotein IIb/IIIa platelet membrane receptorantagonist, recombinant hirudin, thrombin inhibitor (available fromBiogen located in Cambridge, Mass.), and 7E-3B® (an antiplatelet drugfrom Centocor located in Malvern, Pa.). Examples of antimitotic agentsinclude methotrexate, azathioprine, vincristine, vinblastine,fluorouracil, adriamycin, and mutamycin. Examples of cytostatic orantiproliferative agents include angiopeptin (a somatostatin analog fromIbsen located in the United Kingdom), angiotensin converting enzymeinhibitors such as Captopril® (available from Squibb located in NewYork, N.Y.), Cilazapril® (available from Hoffman-LaRoche located inBasel, Switzerland), or Lisinopril® (available from Merck located inWhitehouse Station, N.J.); calcium channel blockers (such asNifedipine), colchicine, fibroblast growth factor (FGF) antagonists,fish oil (omega 3-fatty acid), histamine antagonists, Lovastatin® (aninhibitor of HMG-CoA reductase, a cholesterol lowering drug from Merck),methotrexate, monoclonal antibodies (such as PDGF receptors),nitroprusside, phosphodiesterase inhibitors, prostaglandin inhibitor(available from GlaxoSmithKline located in United Kingdom), Seramin (aPDGF antagonist), serotonin blockers, steroids, thioprotease inhibitors,triazolopyrimidine (a PDGF antagonist), and nitric oxide. Othertherapeutic drugs or agents which may be appropriate includealpha-interferon, genetically engineered epithelial cells, anddexamethasone.

Although the present invention has been described in terms of certainpreferred embodiments, other embodiments that are apparent to those ofordinary skill in the art are also within the scope of the invention.Accordingly, the scope of the invention is intended to be defined onlyby reference to the appended claims. While the dimensions, types ofmaterials and coatings described herein are intended to define theparameters of the invention, they are by no means limiting and areexemplary embodiments.

1. An apparatus for treating a heart, comprising: a medical deviceformed from a metallic alloy and configured to at least partiallysurround the heart; a plurality of electrodes attached to the medicaldevice and having a predetermined spacing; the medical device beingcoated with a dielectric material to electrically insulate the medicaldevice from the electrodes; and the medical device and electrodes beingcompressible to a first delivery configuration small enough to beinserted through an incision in a pericardium, and a second expandedconfiguration wherein the medical device at least partially surroundsthe heart.
 2. The apparatus of claim 1, wherein the electrodes have alength, the electrodes being attached to the medical device so that thelength is adapted to be substantially aligned with a longitudinal axisof the heart.
 3. The apparatus of claim 2, wherein the electrodes areflexible along the length so that the electrodes are adapted tosubstantially conform to a surface of the heart.
 4. The apparatus ofclaim 3, wherein the flexible electrodes have sufficient column strengthto assist in mounting the medical device on the heart.
 5. The apparatusof claim 1, wherein the electrodes are spaced on the medical device sothat at least one electrode is adapted to be positioned adjacent theleft ventricle.
 6. The apparatus of claim 1, wherein the electrodes arespaced on the medical device so that at least one electrode is adaptedto be positioned adjacent the right ventricle.
 7. The apparatus of claim1, wherein the electrodes are spaced on the medical device so that atleast one electrode is adapted to be positioned adjacent the leftventricle and the right ventricle.
 8. The apparatus of claim 1, whereina lead is attached to each electrode.
 9. The apparatus of claim 1,wherein at least one electrode is attached to a power source to providea defibrillating shock to the heart.
 10. The apparatus of claim 1,wherein at least one electrode is attached to a power source to providesensing of the heart.
 11. The apparatus of claim 1, wherein at least oneelectrode is attached to a power source to provide pacing of the heart.12. The apparatus of claim 1, wherein the dielectric material is takenfrom the group of materials consisting of silicone rubber, parylene,polyurethanes, PTFE, TFE, and ePTFE.
 13. The apparatus of claim 1,wherein the medical device is configured to be self-anchoring on theheart.
 14. The apparatus of claim 1, wherein the medical device isconfigured to be self-adjusting on the heart.
 15. The apparatus of claim1, wherein the medical device is configured to be repositioned on theheart.
 16. The apparatus of claim 1, wherein the electrodes areconfigured as electrode rings.
 17. An apparatus for treating a heart,comprising: a medical device formed from a metallic alloy and configuredto at least partially surround the heart; an electrode attached to themedical device; the medical device being coated with a dielectricmaterial to electrically insulate the medical device from theelectrodes; and the medical device and electrode being compressible to afirst delivery configuration small enough to be inserted through anincision in a pericardium, and a second expanded configuration.
 18. Theapparatus of claim 17, wherein the electrode has a length, the electrodebeing attached to the medical device so that the length is adapted to besubstantially aligned with a longitudinal axis of the heart.
 19. Theapparatus of claim 18, wherein the electrode is flexible along thelength so that the electrode is adapted to substantially conform to asurface of the heart.
 20. The apparatus of claim 17, wherein theelectrode is attached to a power source to provide a defibrillatingshock to the heart or is adapted to be used for pacing and sensing theheart.
 21. The apparatus of claim 17, wherein the medical device isconfigured to be self-anchoring on the heart.
 22. The apparatus of claim17, wherein the medical device is configured to be self-adjusting on theheart.
 23. The apparatus of claim 17, wherein the medical device isconfigured to be repositioned on the heart.
 24. The apparatus of claim17, wherein the electrodes are configured as electrode rings.